28 research outputs found
Optical sum-frequency generation in whispering gallery mode resonators
We demonstrate sum-frequency generation in a nonlinear whispering gallery
mode resonator between a telecom wavelength and the Rb D2 line, achieved
through natural phase matching. Due to the strong optical field confinement and
ultra high Q of the cavity, we achieve a 1000-fold enhancement in the
conversion efficiency compared to existing waveguide-based devices. The
experimental data are in agreement with the nonlinear dynamics and phase
matching theory in the spherical geometry employed. The experimental and
theoretical results point to a new platform to manipulate the color and quantum
states of light waves toward applications such as atomic memory based quantum
networking and logic operations with optical signals
Experimental demonstration of interaction-free all-optical switching via the quantum Zeno effect
We experimentally demonstrate all-optical interaction-free switching using
the quantum Zeno effect, achieving a high contrast of 35:1. The experimental
data matches a zero-parameter theoretical model for several different regimes
of operation, indicating a good understanding of the switch's characteristics.
We also discuss extensions of this work that will allow for significantly
improved performance, and the integration of this technology onto chip-scale
devices
Tunable mid-infrared generation via wide-band four wave mixing in silicon nitride waveguides
We experimentally demonstrate wide-band (>100 THz) frequency down-conversion
of near-infrared (NIR) femtosecond-scale pulses from an Er:fiber laser to the
mid-infrared (MIR) using four-wave-mixing (FWM) in photonic-chip
silicon-nitride waveguides. The engineered dispersion in the nanophotonic
geometry, along with the wide transparency range of silicon nitride, enables
large-detuning FWM phase-matching and results in tunable MIR from 2.6-3.6 um on
a single chip with 100-pJ-scale pump-pulse energies. Additionally, we observe >
20 dB broadband parametric gain for the NIR pulses when the FWM process is
operated in a frequency up-conversion configuration. Our results demonstrate
how integrated photonic circuits could realize multiple nonlinear optical
phenomena on the same chip and lead to engineered synthesis of broadband,
tunable, and coherent light across the NIR and MIR wavelength bands from
fiber-based pumps
A six-octave optical frequency comb from a scalable few-cycle erbium fiber laser
A compact and robust coherent laser light source that provides spectral
coverage from the ultraviolet to infrared is desirable for numerous
applications, including heterodyne super resolution imaging[1], broadband
infrared microscopy[2], protein structure determination[3], and standoff
atmospheric trace-gas detection[4]. Addressing these demanding measurement
problems, laser frequency combs[5] combine user-defined spectral resolution
with sub-femtosecond timing and waveform control to enable new modalities of
high-resolution, high-speed, and broadband spectroscopy[6-9]. In this Letter we
introduce a scalable source of near-single-cycle, 0.56 MW pulses generated from
robust and low-noise erbium fiber (Er:fiber) technology, and we use it to
generate a frequency comb that spans six octaves from the ultraviolet (350 nm)
to mid-infrared (22500 nm). The high peak power allows us to exploit the
second-order nonlinearities in infrared-transparent, nonlinear crystals
(LiNbO, GaSe, and CSP) to provide a robust source of phase-stable infrared
ultra-short pulses with simultaneous spectral brightness exceeding that of an
infrared synchrotron[10]. Additional cascaded second-order nonlinearities in
LiNbO lead to comb generation with four octaves of simultaneous coverage
(0.350 to 5.6 m). With a comb-tooth linewidth of 10 kHz at 193 THz, we
realize a notable spectral resolving power exceeding 10 across 0.86 PHz
of bandwidth. We anticipate that this compact and accessible technology will
open new opportunities for multi-band precision spectroscopy, coherent
microscopy, ultra-high sensitivity nanoscopy, astronomical spectroscopy, and
precision carrier-envelope phase (CEP) stable strong field phenomena.Comment: 6 pages, 5 figures. Nat. Photonics (2021
All-fiber frequency comb at 2 {\mu}m providing 1.4-cycle pulses
We report an all-polarization-maintaining fiber optic approach to generating
sub-2 cycle pulses at 2 {\mu}m and a corresponding octave-spanning optical
frequency comb. Our configuration leverages mature Er:fiber laser technology at
1.5 {\mu}m to provide a seed pulse for a thulium-doped fiber amplifier that
outputs 330 mW average power at 100 MHz repetition rate. Following
amplification, nonlinear self-compression in fiber decreases the pulse duration
to 9.5 fs, or 1.4 optical cycles. Approximately 32 % of the energy sits within
the pulse peak, and the polarization extinction ratio is more than 15 dB. The
spectrum of the ultrashort pulse spans from 1 {\mu}m to beyond 2.4 {\mu}m and
enables direct measurement of the carrier-envelope offset frequency using only
12 mW, or ~3.5 % of the total power. Our approach employs only
commercially-available fiber components, resulting in a turnkey amplifier
design that is compact, and easy to reproduce in the larger community.
Moreover, the overall design and self-compression mechanism are scalable in
repetition rate and power. As such, this system should be useful as a robust
frequency comb source in the near-infrared or as a pump source to generate
mid-infrared frequency combs.Comment: corrected typo
Mid-infrared frequency combs at 10 GHz
We demonstrate mid-infrared (MIR) frequency combs at 10 GHz repetition rate
via intra-pulse difference-frequency generation (DFG) in quasi-phase-matched
nonlinear media. Few-cycle pump pulses (15 fs, 100 pJ) from
a near-infrared (NIR) electro-optic frequency comb are provided via nonlinear
soliton-like compression in photonic-chip silicon-nitride waveguides.
Subsequent intra-pulse DFG in periodically-poled lithium niobate waveguides
yields MIR frequency combs in the 3.1--4.1 m region, while
orientation-patterned gallium phosphide provides coverage across 7--11 m.
Cascaded second-order nonlinearities simultaneously provide access to the
carrier-envelope-offset frequency of the pump source via in-line f-2f nonlinear
interferometry. The high-repetition rate MIR frequency combs introduced here
can be used for condensed phase spectroscopy and applications such as laser
heterodyne radiometry
Mid-infrared frequency comb generation via cascaded quadratic nonlinearities in quasi-phase-matched waveguides
We experimentally demonstrate a simple configuration for mid-infrared (MIR)
frequency comb generation in quasi-phase-matched lithium niobate waveguides
using the cascaded- nonlinearity. With nanojoule-scale pulses from
an Er:fiber laser, we observe octave-spanning supercontinuum in the
near-infrared with dispersive-wave generation in the 2.5--3 \text{\mu}m
region and intra-pulse difference-frequency generation in the 4--5
\text{\mu}m region. By engineering the quasi-phase-matched grating profiles,
tunable, narrow-band MIR and broadband MIR spectra are both observed in this
geometry. Finally, we perform numerical modeling using a nonlinear envelope
equation, which shows good quantitative agreement with the experiment---and can
be used to inform waveguide designs to tailor the MIR frequency combs. Our
results identify a path to a simple single-branch approach to mid-infrared
frequency comb generation in a compact platform using commercial Er:fiber
technology
Dual frequency comb spectroscopy in the molecular fingerprint region
Spectroscopy in the molecular fingerprint spectral region (6.5-20 m)
yields critical information on material structure for physical, chemical and
biological sciences. Despite decades of interest and effort, this portion of
the electromagnetic spectrum remains challenging to cover with conventional
laser technologies. In this report, we present a simple and robust method for
generating super-octave, optical frequency combs in the fingerprint region
through intra-pulse difference frequency generation in an orientation-patterned
gallium phosphide crystal. We demonstrate the utility of this unique coherent
light source for high-precision, dual-comb spectroscopy in methanol and ethanol
vapor. These results highlight the potential of laser frequency combs for a
wide range of molecular sensing applications, from basic molecular spectroscopy
to nanoscopic imaging
Infrared electric-field sampled frequency comb spectroscopy
Molecular spectroscopy in the mid-infrared portion of the electromagnetic
spectrum (3--25 um) has been a cornerstone interdisciplinary analytical
technique widely adapted across the biological, chemical, and physical
sciences. Applications range from understanding mesoscale trends in climate
science via atmospheric monitoring to microscopic investigations of cellular
biological systems via protein characterization. Here, we present a compact and
comprehensive approach to infrared spectroscopy incorporating the development
of broadband laser frequency combs across 3--27 um, encompassing the entire
mid-infrared, and direct electric-field measurement of the corresponding near
single-cycle infrared pulses of light. Utilizing this unified apparatus for
high-resolution and accurate frequency comb spectroscopy, we present the
infrared spectra of important atmospheric compounds such as ammonia and carbon
dioxide in the molecular fingerprint region. To further highlight the ability
to study complex biological systems, we present a broadband spectrum of a
monoclonal antibody reference material consisting of more than 20,000 atoms.
The absorption signature resolves the amide I and II vibrations, providing a
means to study secondary structures of proteins. The approach described here,
operating at the boundary of ultrafast physics and precision spectroscopy,
provides a table-top solution and a widely adaptable technique impacting both
applied and fundamental scientific studies
Mid-infrared frequency comb with 6.7 W average power based on difference frequency generation
We report on the development of a high-power mid-infrared frequency comb with
100 MHz repetition rate and 100 fs pulse duration. Difference frequency
generation is realized between two branches derived from an Er:fiber comb,
amplified separately in Yb:fiber and Er:fiber amplifiers. Average powers of 6.7
W and 14.9 W are generated in the 2.9 m idler and 1.6 m signal,
respectively. With high average power, excellent beam quality, and passive
carrier-envelope phase stabilization, this light source is a promising platform
for generating broadband frequency combs in the far infrared, visible, and deep
ultraviolet